The emphasis of the work next year will be to determine how diet composition affects protein and energy utilization. Data will be obtained from rats fed diets with varying proportions of energy nutrients at a given feeding level; selected diet compositions will then be further studied by feeding diets at different levels of intake and determining energy deposition coefficients. Changes in energy deposition coefficients as functions of changes in diet composition will be determined by correlating coefficients and dietary percentages of the energy nutrients. A primary goal of next year's work is to eliminate unintended dietary variables. More specifically, our aim is to devise ways of expressing diet composition that can account for all dietary variables in contrast to controlling for only dietary protein concentration and energy content.